Реферат: Methane joint conversion with higher alkanes on Zn-modified zeolites was first studied few decades ago [1-3], and the possibility of methane involvement into the aromatization reaction was demonstrated. Later on, the pathway of methane transformation to aromatic products was established with the aid of advanced 13C MAS NMR method [4, 5]. It is suggested that this process occurs through the alkylation of aromatic hydrocarbons, formed exclusively from the higher alkanes, by methoxy surface species originated from methane. It is also shown that methane activation on the Zn sites follows the “alkyl” pathway that leads to zinc-methyl species, whereas the only way for the methoxy species to be formed is through zinc-methyl oxidation with O2 impurities [6]. Thus, it was clear that methane conversion to aromatics in nonoxidative conditions is hardly possible considering the established mechanisms. Our recent studies on the properties of Zn-modified BEA zeolite, containing either Zn2+ sites or ZnO clusters, with respect to C3–C4 alkanes aromatization [7, 8] have revealed an interesting peculiarity. During the initial period of n-butane conversion kinetics (Fig. 1a), the amount of methane formed is lower than that of propane. This is unusual observation if one assumes methane and propane are the products of n-butane hydrogenolysis only. To explain such experimental finding, we reasonably suggested there was a rout of methane consumption. It is observable at the initial stage of the alkane conversion (propane and n-butane) and can be described as a complex reaction involving surface intermediates formed from both the alkane and methane and yielding smaller alkanes (ethane and propane, respectively). Importantly, we have obtained spectroscopic evidences of the occurrence of such reaction (Fig. 1b). It was monitored with 13C MAS NMR method that 13C atoms of methane-13C penetrated into the products of n-butane transformation on Zn/H-BEA zeolite to both smaller alkanes and olefins/aromatics. In this report, we present our recent experimental data and discuss this finding in terms of possible mechanism of methane and higher alkanes joint conversion in nonoxidative conditions on Zn-modified zeolites. Acknowledgement. This work was supported by the Russian Science Foundation, grant 19-43-04101, and Deutsche Forschungsgemeinschaft, grant HA 1893/22-1. References: [1] L.B. Pierella, G.A. Eimer, O.A. Anunziata, Stud. Surf. Sci. Catal. 119 (1998) 235. [2] O.A. Anunziata, G.V.G. Mercado, L.B. Pierella, Catal. Lett. 87 (2003) 167. [3] G.V. Echevsky, E.G. Kodenev, O.V. Kikhtyanin, V.N. Parmon, Appl. Catal. A-Gen. 258 (2004) 159. [4] M.V. Luzgin, V.A. Rogov, S.S. Arzumanov, A.V. Toktarev, A.G. Stepanov, V.N. Parmon, Catal. Today 144 (2009) 265. [5] M.V. Luzgin, V.A. Rogov, S.S. Arzumanov, A.V. Toktarev, A.G. Stepanov, V.N. Parmon, Angew. Chem., Int. Ed. 47 (2008) 4559. [6] A.A. Gabrienko, S.S. Arzumanov, M.V. Luzgin, A.G. Stepanov, V.N. Parmon, J. Phys. Chem. C 119 (2015) 24910. [7] A.A. Gabrienko, S.S. Arzumanov, Z.N. Lashchinskaya, A.V. Toktarev, D. Freude, J. Haase, A.G. Stepanov, J. Catal. 391 (2020) 69. [8] S.S. Arzumanov, A.A. Gabrienko, A.V. Toktarev, Z.N. Lashchinskaya, D. Freude, J. Haase, A.G. Stepanov, J. Phys. Chem. C 123 (2019) 30473.

Библиографическая ссылка: Gabrienko A.A. , Lashchinskaya Z.N. , Arzumanov S.S. , Freude D. , Haase J. , Stepanov A.G.
Methane Joint Conversion with Higher Alkanes on Zn-Modified BEA Zeolite: Kinetic and NMR evidences for the Reaction Occurrence in Nonoxidative Conditions
6th International School-Conference on Catalysis for Young Scientists «Catalyst Design: From Molecular to Industrial Level» 16-19 May 2021